by Anne Stuart
In the beginning, there were cameras. Then came flashbulbs. Then came ever-smaller
cameras with attached or built-in electronic flashes. And with them came red-eye
-- that eerie crimson glow in a subject’s eyes. It can make even cutest
kid can look downright diabolical.
Red-eye’s cause is simple: The flash bounces back off the blood vessels
in the subject’s retina; the camera captures both the burst of light
and the reddish hue. Today’s compact cameras exacerbate the problem
because of the proximity of flash unit and lens.
"The closer they are,
the more red-eye you’re going to get," says
Robert Ulichney, a Cambridge, Mass.-based scientist in HP’s Image Systems
Lab and one of the HP Labs researchers working to get the red out.
HP researchers have developed two approaches to detecting and
correcting red-eye. The first exploits an earlier algorithm that
accurately detects faces in photographs or real-time video. The
second is based on a detector trained specifically to find red
A Labs-based implementation of these algorithms led to HP’s
In-Camera Red-Eye Removal, which instantly removes red-eye from
photos while they’re still in the camera, without using
a PC and graphics software -- an industry first.
May in HP's new Photosmart R707 digital
camera, the red-eye removal feature is one of several imaging
technologies that originated in HP Labs and are now appearing
in a line of new HP cameras.
Meanwhile, Ulichney and collaborators J.M. Van Thong, Matthew
Gaubatz, and Huitao Luo, have developed a simple, one-click system
they call RedBot
aimed at making HP’s imaging algorithms even better.
in mid-2003, the scientists tested RedBot on about 1,700 photographs
submitted by HP employees through a company intranet. The algorithms
found and fixed red-eye about 90 percent of the time. "That’s
a very good success rate," Ulichney
says, but researchers want to push the percentages even higher
by running their algorithms on a much larger sample.
employs three algorithms: the original face detector-based one,
the eye detector-based one, and one they acquired from FotoNation
Inc. of San Francisco. Each photo is tested randomly using one
of these algorithms. The Web service logs the details and records
feedback from the user.
The RedBot site, which went public earlier this year, lets
anyone submit a digital picture for free automatic red-eye correction,
a process that usually takes less than one second. In exchange,
RedBot retains a copy of the image for use in evaluating how well
the process worked.
"The number one goal is to improve the algorithms,
and the only way to make it better is to test it," Ulichney
says. Specifically, the team wants to gauge how well each algorithm
detects and fixes red-eye. Researchers are also looking for instances
where the algorithm misses those crimson pupils or registers "false
positives," incorrectly detecting something like a reddish
facial blemish or a Christmas tree light.
An image that is not corrected
is a useful research tool, Ulichney explains. "It’s
valuable when we come across something that causes the algorithm
to fail because it uncovers shortcomings that may not be exposed
IThe team hopes RedBot will harvest at least 10,000 images. To work with
RedBot, photos must be in JPEG format, in files smaller than 3.5 megabytes.
Skip the pictures of dogs, cats,
and other pets; currently, the algorithms are tuned for human eyes only,
Ulichney says. Photo flash reflections in animal eyes are not even red –blue,
green, and yellow hues are common. (All photos collected on RedBot are tested
privately and won’t be publicly displayed.)
Ultimately, HP’s solutions
will provide photographers with an easy alternative to existing red-eye correction
methods which are often ineffective or too difficult for most people to use
Cameras with "pre-flash" capability --
those that flash once to contract the subject’s pupils and again to capture
the image --are problematic because most subjects think they’re done
after seeing the initial light. "Then, when the actual flash comes, the pose
is lost," Ulichney says. Other times, the first, bright flash causes the subject’s
eyes to close. In addition, a flash consumes a significant amount of power,
so eliminating the need for the double flash extends battery life.
Fixing red-eye after photos are downloaded to a PC isn’t an ideal
solution, either. Most photographers aren’t proficient enough with
the graphic arts software to get natural-looking results.
Ultimately, HP will
embed software for red-eye correction technology in all its imaging products,
an initiative that will provide significant competitive advantage in a
rapidly growing market. It will also include the red-eye correction software
in its common user interface for all its products.
By 2008, more
than a billion small (and thus red-eye prone) -- devices, including cell
phones and handheld computers, will take flash photographs, Ulichney notes.
If the team has their way, red-eye will be history by then.